The invention relates to a continuous process for fabricating a paint roller having an extruded plastic core and a hellically-wound absorbent fabric bound to the exterior surface of the core.
Paint rollers are and have been commonly used to apply paints and other coating materials to surfaces for many years. Paint rollers have a unique set of required specifications due to the physical nature of the application process and due to the wide range of paints and other coating materials that the roller may be exposed to in routine use. Paint rollers must have a rigid inner core that is manufactured in a cylindrical shape with a high level of precision so that when the paint roller rotates relative to the surface to be painted, it coats evenly. The cylindrical shape of the roller should not yield, bend or deform under significant stress even when the outer fabric has absorbed paint over an extended period. Even slight deformation of the roller shape may cause uneven paint application.
A manufacturer of paint rollers must assume that the roller could be exposed to any of a wide range of fluid compositions. Some paints are water-based and others are oil or solvent-based. Many different pigments, solubilizing agents, surfactants, viscosifiers, emulsifiers, etc., are used in paints, stains and other surface coating compositions. Ideally, the roller core should be inert or at least resistant to all such ingredients so that its rigid cylindrical shape is maintained even after long periods of use, washing and reuse. A sturdy solvent-resistant core yields a longer effective life-time for the roller which is an important objective for those who buy and use paint rollers.
Paint rollers typically have an absorbent fabric material fixed to the external surface of the core. The fabric should be uniformly absorbent and bonded to the core in a manner which remains in tact when the roller is exposed to paint. The fabric must also be applied and bonded to the core in a precise and continuous configuration so that there is no overlap or gaps in the fabric which could result in a non-uniform paint application pattern.
Various procedures have been used by others to produce paint rollers that satisfy to some extent the specifications discussed above. However, a significant disadvantage with prior manufacturing processes is that they require multiple on and off-line procedures. For example, a desirable core material due to its water and solvent resistivity is extruded plastic such as polyethylene or polypropylene. Typically the core material is extruded, formed and cooled in one process, then put through at least a second process where the core is wrapped with fabric. Multiple on and off-line processing sequences add to manufacturing costs and manual work requirements. Thus, there is a need for a paint roller manufacturing method in which a high quality, solvent-resistant paint roller can be fabricated in a single continuous on-line process.
The invention provides a method, system and apparatus for manufacturing paint rollers through the use of an extruder employing a rotating head so that a plastic core can be extruded and rotated simultaneously while other process steps including application of an outer absorbent material are performed downstream in a single continuous process. The result is a reduction in manufacturing cost compared to prior methods, and a high quality paint roller product, in particular, a solid rigid core that is highly durable and resistant to water and solvents.
In a preferred embodiment of the invention, a cylindrical polypropylene core is extruded. The rotating core then translates through a vacuum sizing and cooling chamber. Next, the core passes through a winding and pulling station which is coordinated with the drive unit of the extruder. The core is subsequently plasma-treated prior to extruding an epoxy adhesive layer on the external surface of the core. Finally, the core is heated, wrapped with fabric and cut into discrete paint rollers. All of the steps are performed in a continuous time- and location-coordinated procedure with minimal if any manual involvement.